Billy Sharp offered no excuses following Friday's loss at Hull City.
The skipper remarked: "We weren't at the races and we didn't start particularly well, despite getting warned by the Gaffer.
"It was the biggest game of the season and we knew that ourselves but give Hull some credit they were at it and wanted it more than us."
The striker conceded: "It was a disappointing result and a disappointing performance, we struggled to get hold of the game.
"We didn't have enough quality on the ball and didn't win the ball back quick enough.
"They managed to take a chance they created and we missed a big opportunity to move into the top six."